1. Field of the Invention
This invention relates to a magnetic disk cartridge. This invention particularly relates to a magnetic disk cartridge comprising a small-diameter, very thin magnetic disk which is rotated at a high speed for recording and reproducing of image information or the like.
2. Description of the Prior Art
Floppy disks are widely used as recording media for computers because they are easy to handle and low in cost. The floppy disk comprises a disk-like base made of a flexible polyester sheet or the like, and magnetic material layers overlaid on opposite surfaces of the disk-like base. The floppy disk is rotated at a high speed for magnetically recording information in the magnetic material layers by use of a magnetic head.
On the other hand, by utilizing the aforesaid advantages of the floppy disk and the advantage that a magnetic recording medium has over silver halide photographic films in that the magnetic recording medium can be reused, it has been proposed to use a magnetic disk having a size smaller than the size of the floppy disk as an image recording medium in still cameras. The magnetic disk used for still cameras comprises a small-diameter, very thin magnetic recording medium, and a hub secured to the center of the magnetic recording medium. The magnetic disk is rotatably housed in a small, hard case provided at the center thereof with a hub hole for exposing the hub of the magnetic disk. The case also has magnetic head insertion apertures for exposing a part of the magnetic disk in the front surface and the rear surface of the case. The combination of the magnetic disk with the case is called a magnetic disk cartridge.
The magnetic disk cartridge of the aforesaid type is provided with a shutter for closing the window sections, through which is inserted a magnetic head, for the purpose of protecting the surfaces of the magnetic disk. The shutter has a U-shaped cross-section and is fitted onto the case so as to grasp the upper and lower surfaces of the case in a manner slidable in a direction approximately normal to the depth direction of the apertures of the window sections. The shutter is urged by a spring member to close the window sections when the magnetic disk is not used for recording and reproducing.
The configuration of the conventional magnetic disk cartridge will further be described with reference to FIGS. 1, 2 and 3.
FIG. 1 is a partial perspective view showing the configuration of the shutter section of the conventional magnetic disk cartridge, and FIG. 2 is a cross-sectional view showing a part of the cross-section taken along line A--A of FIG. 1. A case 1 comprises an upper case half 1a and a lower case half 1b, which have window sections 1c (only one shown) for insertion of a magnetic head in the vicinity of one edge portion of the case 1. Around the window sections 1c are provided step-like sections 1d for receiving the upper side and the lower side of a shutter 2. Thus the window sections 1c and the step-like sections 1d are symmetrically positioned in the upper case half 1a and the lower case half 1b. The shutter 2 is slidably fitted onto the case 1 so as to grasp the step-like sections 1d. The shutter 2 is provided with window sections 2a (only one shown) which are aligned with the window sections 1c when the shutter 2 is positioned in a predetermined sliding position. The lower case half 1b has a pin 1e fabricated integrally with the lower case half 1b in the vicinity of the edge portion of the lower case half 1b where the step-like section 1d exists. Further, the shutter 2 has a hook 2b fabricated integrally therewith. Between the pin 1e and the hook 2b is positioned a spring 3 for urging the shutter 2 to close the window sections 1c.
When the magnetic disk cartridge having the configuration as described above is assembled, one end of the spring 3 is engaged with the pin le provided on the lower case half 1b. The upper case half 1a is aligned with the lower case half 1b from above and mounted thereon so that the spring 3 is grasped between the upper case half 1a and the lower case half 1b. Then, the upper case half 1a and the lower case half 1b are secured to each other by ultrasonic fusion or the like. The other end of the spring 3 is then engaged with the hook 2b provided on the shutter 2, and the shutter 2 is fitted onto the step-like sections 1d of the case 1.
In the aforesaid assembly method, since the spring 3 must be engaged with the lower case half 1b before securing the upper case half 1a to the lower case half 1b and must be engaged with the shutter 2 after the securing step, the efficiency of the assembly work is low and the spring 3 readily disengages from the case half 1b and/or the shutter 2.
FIG. 3 is a partial perspective view showing another configuration of the shutter of the conventional magnetic disk cartridge. In FIG. 3, a hook 1f is provided on at least one of the upper case half 1a and the lower case half 1b. After the upper case half 1a is secured to the lower case half 1b, one end of the spring 3 is engaged with the hook 1f, and the other end thereof is engaged with the hook 2b of the shutter 2. Thereafter, the shutter 2 is fitted onto the case 1. Since securing of the upper case half 1a and the lower case half 1b to each other is conducted by ultrasonic fusion or the like before engagement of the spring 3 with the case 1 and the shutter 2, this method is advantageous from the viewpoint of protecting the magnetic disk cartridge from dust and the efficiency of the assembly work. However, since the ends of the spring 3 are simply hooked on the hooks 1f and 2b, the method has the drawback that the spring 3 will readily separate from the hooks 1f and 2b due to vibration during the assembly work.